WO2016086675A1 - Procédé d'amplification de rétroéclairage de dispositif d'affichage à cristaux liquides (lcd) à mode courant, et circuit - Google Patents

Procédé d'amplification de rétroéclairage de dispositif d'affichage à cristaux liquides (lcd) à mode courant, et circuit Download PDF

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Publication number
WO2016086675A1
WO2016086675A1 PCT/CN2015/085468 CN2015085468W WO2016086675A1 WO 2016086675 A1 WO2016086675 A1 WO 2016086675A1 CN 2015085468 W CN2015085468 W CN 2015085468W WO 2016086675 A1 WO2016086675 A1 WO 2016086675A1
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WO
WIPO (PCT)
Prior art keywords
circuit
current
inductor
lcd backlight
diode
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PCT/CN2015/085468
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English (en)
Chinese (zh)
Inventor
程微
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中兴通讯股份有限公司
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Publication of WO2016086675A1 publication Critical patent/WO2016086675A1/fr

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source

Definitions

  • the present invention relates to the field of communications, and in particular, to a current-type LCD backlight boosting method and circuit.
  • the liquid crystal display (LCD) backlight of a mobile terminal product such as a smart phone or a tablet computer
  • LCD liquid crystal display
  • LEDs Light Emitting Diodes
  • FIG. 1 is a block diagram of a conventional backlight boosting circuit according to the related art.
  • a DC converter Direct Current/Direct Current, abbreviated as DC/DC
  • the current is monitored by detecting the voltage across the current-sampling resistor, and the pulse width and duty cycle of the DC/DC are controlled by an error amplifier to achieve a constant current output.
  • the disadvantage of this scheme is that the current sampling resistor has a current through the power loop, so there is a large theoretical power consumption. For example, in the case of an output voltage of 10 V and a sampling voltage of 0.5 V, the power consumption of the sampling resistor reaches 5% of the output power. It is unfavorable for mobile terminals to reduce power consumption.
  • the conventional scheme is a boost-like DC/DC, and the main difference is error sampling. the way.
  • Conventional DC/DC needs to output a constant voltage, so the error is sampled from the output voltage, and the proportional relationship of the output voltage is obtained by the voltage dividing resistor.
  • the LED backlight circuit requires a constant current to drive, and the error sampling is taken from the voltage of the current sampling resistor. Its voltage is proportional to the current.
  • the present invention provides a current-type LCD backlight boosting method and circuit for solving the above technical problem.
  • a current-type LCD backlight boost circuit includes: an LED current control module, an inductor, a diode, a switching transistor, a capacitor, and an LCD backlight LED display;
  • An LED current control module is connected to the input end of the inductor, configured to measure a voltage of the inductor, and obtain a load current value of the circuit based on the voltage, to adjust the circuit based on the load current value, thereby controlling the LCD backlight LED Display drive current;
  • the inductor has an output connected to the input end of the diode and configured to control current and boost;
  • the diode has an output connected to the input end of the capacitor, configured to be turned on when the induced electromotive force of the inductor charges the capacitor, and turned off when the capacitor is not charged;
  • the switching transistor has an input end connected to the output end of the inductor, and is configured to store the inductor during the conducting period;
  • the capacitor is configured to provide a steady current to the LED
  • the LCD backlight LED display has an input end connected to the input end of the capacitor, and the number of LEDs is related to the screen size of the LCD.
  • the LED current control module includes: an integration circuit, a comparator 1, a comparator 2, an analog multiplier, an error amplifier, a duty ratio measurement circuit, a sawtooth generator, and a timing circuit;
  • the timing circuit is connected to one end of the integrating circuit, the duty ratio measuring circuit, and the sawtooth wave generator, and is set to be timed;
  • the integration circuit has another end connected to the analog multiplier and configured to perform an integration operation
  • the duty ratio measuring circuit is connected to the comparator 1 at the other end thereof, and is configured to measure the second The duty cycle during the turn-on of the pole tube;
  • the analog multiplier is connected at one end to the integrating circuit and the duty ratio measuring circuit, and the other end is connected to the error amplifier, and is arranged to compare an average current during the conducting period of the diode with the duty ratio Multiply, the load current value is obtained.
  • the inductance is a power inductor.
  • the diode is a switching diode or a field effect transistor.
  • the capacitor is a filtered storage capacitor.
  • the present invention also provides a current-type LCD backlight boosting method, wherein the method comprises: measuring a voltage across an inductor in a current-type LCD backlight boost circuit, integrating the voltage to obtain a current And obtaining a load current value of the circuit based on the current value; adjusting the circuit based on the load current value to control a driving current of the LCD backlight LED display in the circuit.
  • adjusting the circuit based on the load current value to control a driving current of the LCD backlight LED display in the circuit comprises: adjusting a conduction period of the switching transistor to achieve a preset desired current value.
  • the invention solves the problem that the theoretical power consumption of the driving circuit of the LCD backlight LED itself is large in the related art, effectively avoids the theoretical power consumption of the driving circuit of the LCD backlight LED, and effectively ensures the stable current of the driving circuit output.
  • FIG. 1 is a block diagram of a conventional backlight boost circuit according to the related art
  • FIG. 2 is a block diagram of a current type LCD backlight boosting circuit according to a first embodiment of the present invention
  • FIG. 3 is a schematic diagram of current waveforms of an inductor according to a second embodiment of the present invention.
  • FIG. 4 is a flow chart of a current type LCD backlight boosting method according to a third embodiment of the present invention.
  • the present invention provides a current-type LCD backlight boosting method and circuit, and the present invention is further detailed in conjunction with the accompanying drawings and embodiments. Description. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
  • FIG. 2 is a block diagram of a current-type LCD backlight boosting circuit according to a first embodiment of the present invention.
  • the circuit includes: an LED current control module, an inductor, a diode, a switching transistor, a capacitor, and an LCD backlight LED display. ;among them,
  • the LED current control module is connected to the input end of the inductor, is configured to measure the voltage of the inductor, and obtain a load current value of the circuit based on the voltage, to adjust the circuit based on the load current value, thereby controlling the driving current of the LCD backlight LED display ;
  • An inductor having an output connected to the input end of the diode and configured to control current and boost; preferably, the inductor can be a power inductor;
  • the diode having an output connected to the input end of the capacitor, configured to be turned on when the induced electromotive force of the inductor charges the capacitor, and turned off when the capacitor is not charged; preferably, the diode is a switching diode or a field effect transistor;
  • a switching transistor having an input connected to an output of the inductor and configured to store energy during conduction
  • the capacitor configured to provide a steady current to the LED; preferably, the capacitor is a filtered storage capacitor;
  • the LCD backlight LED display has an input connected to the input of the capacitor, and the number of LEDs is related to the screen size of the LCD.
  • the LED current control module is described below based on FIG. 2, the module includes: an integration circuit, a comparator 1, a comparator 2, an analog multiplier, an error amplifier, a duty ratio measurement circuit, a sawtooth generator, and a timing circuit;
  • the timing circuit is connected to one end of the integrating circuit, the duty ratio measuring circuit, and the sawtooth wave generator, and is set to be timed;
  • the integration circuit is connected to the analog multiplier at the other end and is set to perform an integral operation
  • a duty cycle measuring circuit the other end of which is connected to the comparator 1 and configured to measure a duty ratio during which the diode is turned on;
  • the analog multiplier has one end connected to the integrating circuit and the duty ratio measuring circuit, and the other end connected to the error amplifier, and is set to multiply the average current during the diode conduction period by the duty ratio to obtain the load current value.
  • the current type LCD backlight boosting circuit further includes a power supply and a power tube driving circuit, and the functions of the two are the same as those in the conventional backlight boosting circuit, and will not be described in detail herein.
  • a current-type LCD backlight boost circuit without a sampling resistor will be described below by way of a preferred embodiment.
  • Mobile terminal products usually use a single-cell lithium battery, and the working voltage is usually between 3V and 4.2V.
  • the backlight LED of the LCD needs a constant current to drive to obtain a pure color temperature.
  • the mobile product is extremely sensitive to power consumption. Therefore, its drive circuit is usually a DC/DC circuit capable of outputting a stable current.
  • the traditional driver circuit block diagram is shown in Figure 1. Because of the existence of the sampling resistor, the theoretical power consumption is the working power. The product of the stream and the sampled voltage. In order to avoid the sampling resistor, a new current control scheme is proposed in the embodiment of the present invention.
  • the current-type LCD backlight boost circuit without sampling resistor includes the following functional modules:
  • LED current control module including: integral circuit, 2 voltage comparators, analog multiplier, error amplifier, duty cycle measuring circuit, sawtooth wave generator;
  • Module C switching diode or replacement device
  • Module D switching transistor or replacement device
  • the module A controls the operating current of the LED by controlling the switching transistor to be turned on and off.
  • the switching transistor can be a bipolar transistor or a field effect transistor, or it can be other controlled electronic switches.
  • module B is a power inductor, which controls the current and boosts. According to the definition of the inductance:
  • the slope of its current change is V/L. If the starting current of each cycle is 0, then the current is an integral of time. Therefore, the current value can be obtained by integrating the voltage across the inductor.
  • the module C is a switching diode, which is turned on when the induced electromotive force of the inductor charges the storage capacitor, and is turned off when the capacitor is not charged, so as to prevent the electric energy from being discharged from other branches.
  • the switching diode can also be replaced by a synchronous switching circuit such as a field effect transistor.
  • Module D is a switching transistor.
  • the module B——inductor is stored, and the inductor current rises.
  • the inductor releases energy through the diode, thereby supplying current to the LED.
  • module E is a filter storage capacitor to provide a stable current to the LED.
  • module F is an electrical load - LCD backlight LED array, its number of LEDs and LCD Screen size and other related.
  • the inductor current at the end of each on-period of the switching transistor is measured by an integrator, and the duty cycle of the diode conduction is also measured and multiplied. The current through the LED is proportional to the product.
  • the technical solution in the embodiment of the present invention is still a boost-like DC/DC, which is similar to the solution in the related art, and the main difference is the LED current control module.
  • the integration circuit integrates the input voltage and is therefore proportional to the inductor current, as follows:
  • the comparator 1 converts the diode-conducted signal into a constant-amplitude pulse signal, and the duty ratio can be measured by, for example, an integrator.
  • the comparator 2 compares the error signal with the sawtooth signal to obtain a pulse width signal that controls the switching transistor.
  • the average current during diode conduction is: I PEAK /2.
  • the duty cycle of the diode conduction is T LED /T ALL , so the average current (ie load current) is the average current ⁇ duty cycle:
  • the duty cycle of the diode conduction is adjusted, so that the load current value reaches the preset desired current value, and the required constant output current can be obtained.
  • FIG. 3 is a schematic diagram of a current waveform of an inductor according to a second embodiment of the present invention.
  • the T FET of FIG. 3 is a switching transistor conduction period. During this period, the current change slope of the inductor is V IN /L. The peak current is I PEAK .
  • the T LED is the diode conduction period. When the diode is turned on, the inductor charges the LED circuit. The slope of the current change is (V OUT -V IN )/L, then the average current during this time is I PEAK /2.
  • T OFF is the switching transistor and the diode are both cut off, this time needs to be greater than 0 to ensure that the current in the inductor returns to 0, to avoid accumulation error;
  • T ALL is a complete cycle. Including the above three periods, the current of the LED is equal to the average current during the diode conduction period multiplied by the duty ratio of its conduction.
  • the peak current also becomes larger, and the diode conduction period also becomes longer, then the LED current becomes larger, and the LED current becomes smaller.
  • FIG. 4 is a flowchart of a current-type LCD backlight boosting method according to Embodiment 3 of the present invention. As shown in FIG. 4, the method includes the following steps. (Step S402 - Step S406):
  • Step S402 measuring a voltage across the inductor in the current-type LCD backlight boost circuit, and integrating the voltage to obtain a current value
  • Step S404 obtaining a load current value of the circuit based on the current value
  • Step S406 adjusting the circuit based on the load current value to control the driving current of the LCD backlight LED display in the circuit.
  • the load current of the circuit is obtained based on the current value, which can be realized by calculating the slope of the current change during the on-time of the switching transistor in the calculation circuit; and calculating the slope of the current when the switching transistor is turned on, according to the slope of the current change, flowing through the inductor
  • step S406 the circuit is adjusted based on the load current value to control the driving current of the LCD backlight LED display in the circuit, which can be realized by adjusting the conduction period of the switching transistor so that the load current value reaches the preset expectation. Current value.
  • the present invention relates to a constant current output DC/DC circuit without a current sampling resistor for driving a backlight LED of a mobile terminal LCD. It is an object of the present invention to reduce the theoretical power consumption of the drive circuit of the LCD backlight LED itself while ensuring that the drive circuit outputs a stable current.
  • the current-type LCD backlight boosting method and circuit provided by the embodiments of the present invention have the following beneficial effects: solving the problem that the theoretical power consumption of the driving circuit of the LCD backlight LED itself is large in the related art, and effectively avoiding the LCD The theoretical power consumption of the driving circuit of the backlight LED effectively ensures that the driving circuit outputs a stable current.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Dc-Dc Converters (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)

Abstract

La présente invention porte sur procédé d'amplification de rétroéclairage de dispositif d'affichage à cristaux liquides (LCD) à mode courant, et un circuit. Le circuit comprend un module de commande de courant de diode électroluminescente (DEL), un inducteur, une diode, un transistor de commutation, un condensateur, et un réseau de DEL de rétroéclairage de LCD. Le module de commande de courant de DEL est connecté à une extrémité d'entrée de l'inducteur, et est configuré pour mesurer la tension de l'inducteur et obtenir une valeur de courant de charge du circuit selon la tension, de manière à régler le circuit selon la valeur de courant de charge, ce qui permet de commander le courant d'attaque du réseau de DEL à rétroéclairage de LCD . Au moyen de la présente invention, le problème selon lequel la consommation d'énergie théorique d'un circuit d'attaque de DEL d'une DEL à rétroéclairage de LCD est grande dans l'état de l'art est résolu, et la consommation d'énergie théorique du circuit d'attaque de DEL à rétroéclairage de LCD est efficacement évitée, ce qui permet d'assurer efficacement que le circuit d'attaque délivre en sortie un courant stable.
PCT/CN2015/085468 2014-12-02 2015-07-29 Procédé d'amplification de rétroéclairage de dispositif d'affichage à cristaux liquides (lcd) à mode courant, et circuit WO2016086675A1 (fr)

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CN201410720126.6 2014-12-02
CN201410720126.6A CN105722283A (zh) 2014-12-02 2014-12-02 一种电流型lcd背光升压方法、电路

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CN112688739A (zh) * 2020-12-16 2021-04-20 武汉永鼎光通科技有限公司 一种自适应背光的apc控制电路

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CN102932985A (zh) * 2011-08-12 2013-02-13 瑞鼎科技股份有限公司 发光二极管驱动装置
CN103400560A (zh) * 2013-08-12 2013-11-20 深圳市华星光电技术有限公司 Led背光驱动电路以及液晶显示器
CN103531147A (zh) * 2013-10-25 2014-01-22 无锡中星微电子有限公司 Led驱动电路及使用该驱动电路的led驱动系统

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